It is a common practice to deploy sonobuoys and other devices from aircraft launching systems to place them in remote locations for detection and signaling purposes. For example, sonobuoys are deployed in remote parts of the ocean for oceanographic survey purposes. In prior practice, a single sonobuoy is ejected from a launching tube by a propulsion device such as a compressed gas cartridge. The launching tube served as a storage container for the sonobuoy as well as a tube for launching the sonobuoy from an aircraft. Certain standard sizes of sonobuoys evolved and the typical larger size is about three feet in length and five inches in diameter. In order to launch a sonobuoy of such size with sufficient velocity to clear the aircraft, a diaphragm is attached to the rear end of the sonobuoy so that the explosive cartridge causes a pressure build-up to eject the sonobuoy from the tube. For this purpose, a sealing relationship is provided between the wall of the tube and the body of the sonobuoy to contain the gas pressure until the sonobuoy has been accelerated to ejection velocity. The acceleration is resisted by the inertia of the sonobuoy as well as the atmospheric air pressure in the muzzle end of the launching tube.
More recent developments in the design and application of sonobuoys have resulted in sonobuoys of much smaller size. It has become desirable, in some applications, to deploy several sonobuoys of relatively small size from a single launching tube. For this purpose, it is known to use a launching tube of the standard size previously used for large sonobuoys and to load several small sonobuoys into the tube for sequential launching. Such a sequential sonobuoy launching system is disclosed in the Woodruff et al U.S. Pat. No. 4,026,188 granted May 31, 1977. In this system, a plurality of similar sonobuoys are loaded in a single launching tube in an end-to-end relationship between the muzzle end and the breech end of the launching tube. A closed bulkhead is provided at the breech end and a separate launching mechanism is provided for each of the sonobuoys. The launching mechanism for each sonobuoy is disposed between its aft end and the forward end of the adjacent sonobuoy, except for the sonobuoy adjacent the bulkhead; for it, the launching mechanism is disposed between the aft of the sonobuoy and the bulkhead. Each launching mechanism comprises a compressed gas cartridge and an explosive squib for piercing the cartridge when actuated by an electrical signal. An electric circuit is provided for actuating the launching mechanisms separately so that the sonobuoys may be ejected from the launching tube one at a time. At the forward end of each sonobuoy is a bulkhead which cradles the sonobuoy and engages the inner cylindrical surface of the launching tube to form a substantially gas tight seal. The aft end of each sonobuoy is cradled by an aft bulkhead which also forms a substantially gas tight seal with the periphery of the launching tube. This arrangement is said to facilitate the launching of a sonobuoy, in that it tends to contain the gas pressure released from the explosive cartridge until the sonobuoy leaves the muzzle of the launching tube.
A similar arrangement for sequential launching of plural sonobuoys is shown in the Ouellette U.S. Pat. No. 4,164,887 granted Aug. 21, 1979. In this system, a firing module is positioned behind each of the buoys. The firing module includes a cup-shaped member with a compressed gas cartridge and firing squib therein. An apertured spacer disk is disposed over the cup-shaped member and is held by stops extending through the wall of the launching tube. The aperture in the spacer disk is said to permit gas from the cartridge to completely fill the region between the module and the sonobuoy to eject it from the launching tube.
A general object of this invention is to provide an improved propulsion means for expelling individual units from a launch tube and to overcome certain disadvantages of the prior art.